One of the benefits of professional domain name providers and web hosting services is the customized email address function. With Yahoo Domains and Yahoo Web hosting you can create a customized email address that goes directly to the domain name of your choice.
An example is if you register the domain name Jonesconsultinggroup.com, you can set up custom email addresses such as James.Jones@jonesconsultinggroup.com instead of using free email services such as yahoo or google mail.
This provides a much more professional image than being forced to use your personal email address (which is often less than ideal) as your business email address as well.
I have hard time taking any business proposition seriously that comes from an email address like Jimmyboy1971@yahoo.com.
This is also why free hosting services such as Myspace, Tripod, or Geocities provide limited functionality.